1. Field of the Invention
The present invention relates to a process for producing an aminonitropyridine by a direct amination reaction of a nitropyridine using an O-substituted hydroxylamine or a salt thereof.
2. Description of the Related Art
An aminonitropyridine can be a precursor of a diaminopyridine and is an important compound as an intermediate of drugs and agricultural chemicals. As the process for synthesizing an aminonitropyridine from a nitropyridine, there has generally been known a process via a substitution reaction between a halogenated nitropyridine and an amine. However, such a process has the disadvantages of having a large number of steps and the requirement of a halogenation step causing high corrosion and a large environmental load.
Some attempts to directly produce an aminonitropyridine from a nitropyridine have been made. However, for example, a process of direct amination of a nitropyridine using a hydroxylamine hydrochloride salt (J. Am. Chem. Soc. 78, 423 (1956)) is not satisfactory because of the reaction yield. In addition, a process of directly aminating a nitropyridine using ammonia and potassium permanganate (Liebigs Ann. Chem. 875 (1991)) has the drawback that a complicated operation is required because one or more equivalents of explosive potassium permanganate is used. A process using 1-sulphenamoylthiocarbonylpyrrolidine as an amination agent (Japanese Laid-Open Patent Publication No. 7-109260) is inferior in industrial utility because the amination agent is expensive.